Rare 6-Million-Year-Old Skull of Juvenile Ape Discovered

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An extremely rare juvenile skull of an extinct ape has now been
revealed from China, findings that suggest a very diverse group
of apes once lived in Southeast Asia, researchers say.

Apes, which include gorillas,
chimpanzees and orangutans, are the closest living relatives
of humanity. They once inhabited most of the Old World, including
large portions of Europe and Asia, and a much larger swath of
Africa than they do at present.

"Climate and environments were changing rapidly throughout the
world at the end of the Miocene, and these changes are reflected
in the changing faunas, particularly in the Old World, where
animals adapted to living in more equable forest habitats gave
way in most places to those capable of living in more open
habitats and drier, more seasonal conditions," said researcher
Jay Kelley, a paleoanthropologist at the Institute of Human
Origins at Arizona State University in Tempe.

Cool cranium discovery

To explore ape evolution during the late Miocene, scientists
investigated a site in the Yunnan province in southern China
called Shuitangba, which is a mine for lignite, a form of
low-grade coal. Southern China was less affected by the
deteriorating climate during the late Miocene that drove extinct
many ape species throughout the rest of Eurasia.

Miners have recovered fossils at Shuitangba since at least the
1950s. The investigators began excavating at the site in 2007.
"The workers keep a lignite fire going all the time to roast
potatoes, which is smoky and smells awful, and your hair and
clothes become permeated with the lignite smell," Kelley said.

"It's from a young juvenile — it would have been perhaps about 5
years old if its growth was like that of
chimpanzees," Kelley told LiveScience. "I suspect adults of
this species would have been in the body size range of large
chimpanzees, the larger males perhaps somewhat larger. We know
from the developing canine teeth that our juvenile was a male."

Back when these apes were alive, the area was fairly swampy —
"warm or hot and wet for much of the year, even if there was some
seasonality," Kelley said. "We have also found a diverse array of
birds associated with wetter environments, and mammals associated
with wet environments such as beavers and otters. We have also
uncovered the trunks of very large trees, so it was heavily
forested."

Learning about ape evolution

Skulls of
fossil apes and other close relatives of humanity are
extremely rare, especially those of infants and young juveniles.
This find is only the second relatively complete cranium of a
young juvenile from the Old World during the entire Miocene, an
epoch stretching from 5 million to 23 million years ago.

"The preservation of the new cranium is excellent," Kelley said
in a statement. "This is important because all previously
discovered adult crania of the species to which it is assigned,
Lufengpithecus lufengensis, were badly crushed and
distorted during
the fossilization process."

In living species of apes, skulls at the same stage of
development as the new fossil already closely resemble those of
adults. "Therefore, the new cranium, despite being from a
juvenile, gives researchers the best look at the cranial anatomy
of Lufengpithecus lufengensis," Kelley said.

Due to where and when Lufengpithecus lived, scientists
had thought it was related to the
modern orangutan, which is now limited to Southeast Asia, but
once also dwelled in southern China. However, the new skull bears
little resemblance to living orangutans.

"More similarity to orangutans would have been expected," Kelley
said.

As such, the researchers now suggest Lufengpithecus
represents a late-surviving lineage of Eurasian apes without
clear links to living groups of apes.

"It increasingly appears that there was a very diverse radiation
of apes surviving in southeastern Asia long after apes had become
extinct in most of the rest of Eurasia," Kelley said.

The researchers hope further excavations will unearth remains of
adult specimens to better uncover the relationships between this
lineage and other fossil and living apes.

"There is a natural tendency among paleoanthropologists to want
one's discovery to be relevant to human evolution, but I don't
think that's the case here," Kelley said. "The evolution of apes
is equally fascinating and to that our new cranium can make a
valuable contribution."

The scientists will detail their findings in print in November in
the journal Chinese Science Bulletin.